Height Factor Zoning in NYC is a set of zoning regulations that results in tall skinny buildings with more open space on their zoning lots. Height Factor buildings can be built in non contextual R6 through R9 zoning districts. Height Factor Zoning is based on the Tower In The Park concept of building design.
Height Factor Zoning has 3 variables that are are linked
- Floor Area Ratio
- Open Space Ratio
- Number of Stories
When the number of stories change the other two factors change with it.
Floor Area Ratio
Floor Area Ratio is a simple formula for determine how many square feet you can build on a property. We have another post on Floor Area Ratio if you want to read more about that concept. the Floor Area Ratio is a factor identified in the zoning code that when multiplied by the lot area determines the building square footage.
Floor Area Ration (FAR) X Lot Area = Buildable Floor Area
In Height Factor Zoning the Floor Area Ratio changes based on the number of stories. This actually leads to a lot of confusion for people because they may see that a certain zoning district has a maximum floor area of X but that floor area Ratio can only be achieved with a specific number of stories.
Open Space Ratio
Height Factor Buildings promote tall skinny buildings. In fact the taller the building the skinnier it gets. The open space ratio regulates how wide a building can be. The open space ratio formula is a percentage of the building floor area that result in the square footage of the open space.
Open Space Ratio OSR% of Building Floor Area (in Square feet) = Square Footage of required open space on the property.
We have another blog post you can read that goes deeper into Open Space Ratio.
Optional Zoning Regulations
Height Factor Zoning is an option. Any residential zoning district where you can apply height factor also has the option of Quality Housing Program Zoning Regulations. You get to choose what zoning you want in R6 through R9 as ling as you are not in a contextual zoning district. Contextual Zoning requires Quality Housing and does not allow Height Factor. So you get to pick you zoning option they both have their advantages and disadvantages.
One key difference between the two zoning options is that Height Factor results in tall skinny buildings and Quality Housing results in shorter wider buildings.
Height Factor Zoning Specifications
The following districts have the optional Height Factor Regulation.
- R6
- R7
- R8
- R9
R6 Height Factor Zoning
| Number Of Stories | Open Space Ratio | Floor Area Ratio |
|---|---|---|
| 1 | 27.5 | 0.78 |
| 2 | 28 | 1.28 |
| 3 | 28.5 | 1.62 |
| 4 | 29 | 1.85 |
| 5 | 29.5 | 2.02 |
| 6 | 30 | 2.14 |
| 7 | 30.5 | 2.23 |
| 8 | 31 | 2.3 |
| 9 | 31.5 | 2.35 |
| 10 | 32 | 2.38 |
| 11 | 32.5 | 2.4 |
| 12 | 33 | 2.42 |
| 13 | 33.5 | 2.43 |
| 14 | 34 | 2.43 |
| 15 | 34.5 | 2.43 |
| 16 | 35 | 2.42 |
| 17 | 35.5 | 2.42 |
| 18 | 36 | 2.4 |
| 19 | 36.5 | 2.39 |
| 20 | 37 | 2.38 |
| 21 | 37.5 | 2.36 |
| Over 21 Stories | 37.5 +.5 per story over 21 | HF FAR Formula |
In R6 Zoning in order to achieve the maximum floor area ratio of 2.43 you must build a 13, 14, or 15 story building. This is going to be an uncommon situation because it would only be feasible on very large lots. In R6 you are more likely to do Quality Housing Program.
R6 Zoning Example:
Lets assume we have a site that is 100 feet by 100 feet. This gives us a lot area of 10,000 square feet.
Assuming we are planning a 13 story building we get an FAR of 2.43.
2.43 x 10,000 = 24,300 square feet for our building.
Our Open Space Ratio is 33.5 so we need 33.5% of 24,300 for our open area.
24,300 x .335 =8,140.5 square feet, that is our open space.
10,000 sq ft – 8,140.5 = The building can be 1,859.5 square feet per floor.
So in this scenario we get a 13 story building with 1,859.5 square feet per floor on a 10,000 square foot lot as long as it does not go over 24,300 square feet. Like I said tall and skinny.
R7 Height Factor Zoning
In R7 Zoning in order to achieve the maximum floor area ratio of 3.44 you must build a 14 story building.
| Number Of Stories | Open Space Ratio | Floor area Ratio |
|---|---|---|
| 1 | 15.5 | 0.87 |
| 2 | 16 | 1.52 |
| 3 | 16.5 | 2.01 |
| 4 | 17 | 2.38 |
| 5 | 17.5 | 2.67 |
| 6 | 18 | 2.88 |
| 7 | 18.5 | 3.05 |
| 8 | 19 | 3.17 |
| 9 | 19.5 | 3.27 |
| 10 | 20 | 3.33 |
| 11 | 20.5 | 3.38 |
| 12 | 21 | 3.41 |
| 13 | 21.5 | 3.42 |
| 14 | 22 | 3.44 |
| 15 | 22.5 | 3.42 |
| 16 | 23 | 3.41 |
| 17 | 23.5 | 3.4 |
| 18 | 24 | 3.38 |
| 19 | 24.5 | 3.36 |
| 20 | 25 | 3.33 |
| 21 | 25.5 | 3.3 |
| Over 21 Stories | 25.5 + .5 per story over 21 | HF FAR Formula |
R7 Zoning Example:
Lets assume we have a site that is 100 feet by 100 feet. This gives us a lot area of 10,000 square feet.
Assuming we are planning a 14 story building we get an FAR of 3.44.
3.44 x 10,000 = 34,400 square feet for our building.
Our Open Space Ratio is 22 so we need 22% of 34,400 for our open area.
34,400 x .22 =7,568 square feet, that is our open space.
10,000 sq ft – 7,568 sq ft = The building can be 2,432 square feet per floor.
So in this scenario we get a 14 story building with 2,432 square feet per floor on a 10,000 square foot lot as long as the building does not exceed 34,400 square feet.
R8 Height Factor Zoning
In R8 Zoning in order to achieve the maximum floor area ratio of 6.02 you must build a 17, 18, 19, or 20 story building.
| Number Of Stories | Open Space ratio | Floor Area Ratio |
|---|---|---|
| 1 | 5.9 | .94 |
| 2 | 6.2 | 1.78. |
| 3 | 6.5 | 2.51 |
| 4 | 6.8 | 3.14 |
| 5 | 7.1 | 3.69 |
| 6 | 7.4 | 4.15 |
| 7 | 7.7 | 4.55 |
| 8 | 8 | 4.88 |
| 9 | 8.3 | 5.15 |
| 10 | 8.6 | 5.38 |
| 11 | 8.9 | 5.56 |
| 12 | 9.2 | 5.71 |
| 13 | 9.5 | 5.81 |
| 14 | 9.8 | 5.92 |
| 15 | 10.1 | 5.95 |
| 16 | 10.4 | 5.99 |
| 17 | 10.7 | 6.02 |
| 18 | 11 | 6.02 |
| 19 | 11.3 | 6.02 |
| 20 | 11.6 | 6.02 |
| 21 | 11.9 | 5.99 |
| Over 21 Stories | 11.9 + .3 per story over 21 | HF FAR Formula |
R8 Zoning Example:
Lets assume we have a site that is 100 feet by 100 feet. This gives us a lot area of 10,000 square feet.
Assuming we are planning a 17 story building we get an FAR of 6.02
6.02 x 10,000 = 60,200 square feet for our building.
Our Open Space Ratio is 10.7 so we need 10.7% of 60,200 for our open area.
60,200 x .107 =6,441.4 square feet, that is our open space.
10,000 sq ft – 6,441.4 sq ft = The building can be 3,558.6 square feet per floor.
So in this scenario we get a 17 story building with up to 3,558.6 square feet per floor on a 10,000 square foot lot as long as the total building does not go over 60,200 square feet.
R9 Height Factor Zoning
In R9 Zoning in order to achieve the maximum floor area ratio of 7.52 you must build a 14, 15, 16, or 17 story building.
| Number Of Stories | Open Space Ratio | Floor area Ratio |
|---|---|---|
| 1 | 1 | .99 |
| 2 | 1.4 | 1.95 |
| 3 | 1.8 | 2.85 |
| 4 | 2.2 | 3.68 |
| 5 | 2.6 | 4.42 |
| 6 | 3.0 | 5.08 |
| 7 | 3.4 | 5.65 |
| 8 | 3.8 | 6.13 |
| 9 | 4.2 | 6.54 |
| 10 | 4.6 | 6.85 |
| 11 | 5 | 7.09 |
| 12 | 5.4 | 7.3 |
| 13 | 5.8 | 7.41 |
| 14 | 6.2 | 7.52 |
| 15 | 6.6 | 7.52 |
| 16 | 7.0 | 7.52 |
| 17 | 7.4 | 7.52 |
| 18 | 7.8 | 7.46 |
| 19 | 8.2 | 7.41 |
| 20 | 8.6 | 7.35 |
| 21 | 9 | 7.25 |
| Over 21 Stories | 9 + .4 per story over 21 | HF FAR Formula |
R9 Zoning Example:
Lets assume we have a site that is 100 feet by 100 feet. This gives us a lot area of 10,000 square feet.
Assuming we are planning a 14 story building we get an FAR of 7.52
7.52 x 10,000 = 75,200 square feet for our building.
Our Open Space Ratio is 6.2 so we need 6.2% of 75,200 for our open area.
75,200 x .062 = 4,662.4 square feet, that is our open space.
10,000 sq ft – 4,662.4 sq ft = The building can be 5,337.6 square feet per floor.
So in this scenario we get a 14 story building with up to 5,337.6 square feet per floor on a 10,000 square foot lot as long as the building does not exceed 75,200 square feet.
Height Factor Zoning in NYC
Height Factor comes from the 1961 Zoning Resolution of New York City. In fact we are still using the 1961 Zoning Resolution except that they regularly update it and have many amendments since 1961.
Tower In The Park
Tower in the Park is a modernist idea for building design started by Architect Le Corbusier. The idea is that a city should have lots of open space with green areas and this is achieved with tall skinny buildings. Tower in the Park can be observed in many Housing Projects around NYC where they have several tall buildings in open green areas. This was a popular mid 20th Century idea.
Height Factor Zoning
As an architect I study Building and Zoning Codes closely, but these are complicated and quite involved issues. In this article we reviewed some of the basic concepts with regards to the Height Factor within the NYC Zoning Resolution. This post does not assume to cover every possible issue or condition, but provide a general overview of the topic.
Thank You for reading our post on Height Factor Zoning.
If you have questions or comments please feel free to leave them below. If you would like to speak with an architect please feel free to contact us directly.
This post was written by Jorge Fontan AIA a Registered Architect and owner of New York City architecture firm Fontan Architecture. Jorge Fontan has earned 3 degrees in the study of architecture including two degrees from the City University of New York and a Masters Degree in Advanced Architectural Design from Columbia University. Jorge has a background in construction and has been practicing architecture for 20 years where he has designed renovations and new developments of various building types.
